1. Technical Field
The present disclosure relates to an electronic device case and a method for treating the surface of the electronic device case, and more particularly, to an electronic device case and a surface treatment method thereof, for enabling uniform coloring of a diecast aluminum alloy surface in various hues.
2. Description of the Related Art
In general, the exterior case of an electronic device is manufactured from plastic, a magnesium alloy, or an aluminum alloy. In particular, the exterior case of a portable electronic device should be lightweight and have good corrosion resistance, good shock resistance, and high yield strength in view of the harsh environment expected from portability. For exterior cases of various looks and sophisticated designs, a number of surface finishes should be possible.
A plastic surface, however, is vulnerable to scratches and has a low strength. Moreover, plastic cannot shield electromagnetic waves emitted from an electronic device. That's why aluminum or magnesium is usually used for the exterior case of a portable electronic device. Pressing or diecasting are manufacturing methods suitable for molding an aluminum or magnesium exterior case.
A conventional technology for press-molding an aluminum alloy is disclosed in Korea Laid-Open Publication No. 10-2009-0130259 (published on Dec. 21, 2009) entitled “Aluminum Alloy Plate for Press Molding”.
However, if an electronic device case is molded by press molding, it is difficult to manufacture the electronic product comprising the case into a complex shape. Therefore, diecasting is more popular in manufacturing an exterior case of a relatively complex shape.
Conventional technologies for a diecast aluminum alloy and surface treatment of an electronic device using the same are disclosed in Korea Patent No. 10-0852144 (registered on Aug. 7, 2008) entitled “Die Casting Aluminum Alloy for Frame of Mobile Electronic Equipment and Painting Method for Frame Using the Same” and Korea Patent No. 10-1016278 (registered on Feb. 14, 2011) entitled “Method of Surface Treatment for Die Casting Materials for Mobile Phone Case, and the Structure”.
However, a diecast aluminum alloy surface is chemically nonuniform due to external exposure of an Si component included in the aluminum alloy, is nonuniform in its crystal structure due to coagulation, or is physically nonuniform, such as pores caused by air introduced during pressing. As a result, the surface of an exterior case is difficult to paint in an intended sophisticated hue and to color through anode oxidation coating.
Although a aluminum alloy component is controlled in cast of diecast to prevent the diecast aluminum alloy surface from being nonuniform, this decreases the strength of the diecast aluminum alloy.
To facilitate surface finishes including painting or plating on the diecast aluminum alloy surface, an aluminum layer is deposited and then the surface of the aluminum layer is subjected to anode oxidation. However, because aluminum on the aluminum alloy surface is very vulnerable to corrosion and has a low strength, the adhesive strength of the aluminum layer is reduced after anode oxidation coating. Consequently, pigment coloring, plating, and painting of the surface of the oxidized coating layer are not easily performed in a manner that achieves a desired quality finish. A colored or painted layer can be easily peeled off from the aluminum layer, which makes it difficult to commercialize anode oxidation on a diecast aluminum alloy surface.